This invention relates in general to a deviation driver circuit which is capable of producing a difference voltage having a magnitude related to the voltage of a deviation signal provided to the circuit from an external source. In particular, the deviation driver circuit of the present invention is comprised of a first differential amplifier to which a second differential amplifier and a multiple input integrator are interconnected to provide negative feedback.
In order to eliminate induced noise and/or ground noise from the difference voltage produced by the deviation driver circuit, it is necessary to have the deviation driver circuit present a large impedance to ground. Transformer coupled signals have been used in the prior art to produce this high impedance to ground. This coupling technique includes rectifying the transformer output signals to provide a DC signal and then driving this DC signal through fairly large resistors. While this coupling technique effectively produces a large impedance to ground, it also increases the differential impedance of the deviation driver circuit. As a result, dummy loads must be utilized to keep the output signal constant and any change in the value of the dummy loads will cause an inaccurate output. Accordingly, the operation of this circuit is continuously monitored in order to insure its accuracy.
It is therefore an object of the present invention to provide a deviation driver circuit which exhibits not only a high impedance to ground to keep induced noise and/or ground noise from appearing in difference voltage produced by this circuit but also a low differential impedance to eliminate the need for dummy loads. The deviation driver circuit of the present invention is comprised of a first differential amplifier having a second differential amplifier and a multiple input integrator coupled with it to form a negative feedback loop. The first differential amplifier provides the high impedance to ground needed to keep induced noise and/or ground noise from appearing in the difference voltage produced by this circuit. The second differential amplifier, on the other hand, is arranged to lower the differential impedance of the deviation driver circuit while the multiple input integrator is provided to maintain the stability of the feedback loop.
Another object of the present invention is to provide a deviation driver circuit which is capable of being connected directly to external equipment without the need for additional coupling circuits.
Another object of the present invention is to provide a deviation driver circuit which is capable of maintaining a positive common mode voltage at its output terminals.
Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description of the drawing.